Prepare Cream Cheese Icing; cover and chill.
Coat bottoms of 3 (9-inch) round cake pans with cooking spray (do not coat sides of pans); line bottoms of pans with wax paper. Coat wax paper with cooking spray, and dust with flour; set aside.
Combine sugar and butter in a large bowl; beat at medium speed of a mixer until well-blended. Add egg yolks, 1 at a time, beating well after each addition. Combine 2 cups flour and baking soda; stir well. Add flour mixture to creamed mixture alternately with buttermilk, beginning and ending with flour mixture. Stir in pecans and extracts.
Beat egg whites at high speed of a mixer until stiff peaks form (do not overbeat). Fold egg whites into batter; pour batter into prepared pans. Bake at 350° for 23 minutes. Let cool in pans 5 minutes on a wire rack. Loosen cake layers from sides of pans using a narrow metal spatula, and turn out onto wire racks. Peel off wax paper, and let cool completely.
Place 1 cake layer on a plate, and spread with 2/3 cup Cream Cheese Icing; top with another cake layer. Repeat with 2/3 cup icing and remaining layer, ending with cake. Spread remaining icing over cake. Garnish with kumquats, orange rind, and kumquat leaves, if desired.
Note: To make sugared kumquats, dip kumquats into lightly beaten egg whites, and drain; roll in sugar.